Intracellular recording combined with intracellular HRP injection, light and electron microscopy will be used to study the organization of synaptic terminals arising from striatal afferents on the somatic and dendritic surface of single identified spiny projection neurons of rat striatum. Lesions in cerebral cortex, intralaminar nucleus of the thalamus or substantia nigra will be used both to examine their contributions to synaptic potentials evoked by stimulation of remaining afferents (i.e. by means of axon reflexes, disynaptic pathways, etc.), and to identify the distribution of terminal boutons from individual afferent systems on the same HRP-injected spiny neurons. These experiments are intended to yield evidence concerning the relative effectiveness of each striatal afferent pathway in governing the activity of spiny neurons, and so to contribute to the understanding of neuronal integration in this direct route for information flow through striatum.